CN Pat. Appl. No. 94113403.2 (Filing Date: Dec. 30, 1994) teaches a synthesis of ZSM-5 and ZSM-11 co-crystalline zeolite containing rare earth element, which is different from the zeolite described in U.S. Pat. No.4,229,424. This zeolite has a weight ratio of ZSM-5 crystalline structure portion to ZSM-11 crystalline structure portion in the range of 0.05 to 20; and in its originally synthesized anhydrous state a chemical composition formula in terms of mole ratios of oxides as follows: EQU XNa.sub.2 O.YRE.sub.2 O.sub.3.Al.sub.2 O.sub.3.ZSiO.sub.2
wherein X is within the range of 0.1 to 1.0, Y is within the range of 0.1 to 1.0, and Z is within the range of 20 to 300; and its adsorption capacities range from 9 to 11 wt %, from 3 to 4 wt % and from 4 to 8 wt % respectively for n-hexane, cyclohexane and water, and provides an X-ray diffraction pattern comprising the following X-ray diffraction lines and assigned relative intensities;
______________________________________ d(A) 100 I/I.sub.o ______________________________________ 11.2 .+-. 0.2 M 10.1 .+-. 0.2 M 6.05 .+-. 0.14 W 4.40 .+-. 0.08 W 3.86 .+-. 0.07 VS 3.72 .+-. 0.07 S 3.65 .+-. 0.07 W-M 2.01 .+-. 0.02 W ______________________________________ VS = very strong (100-60); S = strong (60-40); M = medium (40-20); W = weak (&lt;20)
The processes for preparing ethyl benzene by alkylation of benzene with ethylene can be generally divided into three kinds, namely liquid-phase AlCl.sub.3 process, BF.sub.3 process and vapor-phase silicate zeolite process. The catalyst used in vapor-phase silicate zeolite process is zeolite catalyst, which normally is Pentasil type zeolite or ZSM series zeolite catalyst. For example, U.S. Pat. No. 4,107,224 discloses a process for manufacturing ethyl benzene from benzene and dilute ethylene raw materials, in which the reaction conditions include a temperature ranging from 250 to 600.degree. C., a pressure ranging from 0.1 to 100 atmospheres, a feedstock weight hourly space velocity ranging from 0.1 to 100 hr.sup.-1, a molar ratio of benzene to ethylene ranging from 1 to 30 and a catalyst containing a ZSM-5, -11, -12, -35 or -38 zeolite. Like the previous techniques in the prior art this process has comparatively strict requirement for contents of impurities in the raw materials. The raw material gas must contain no such acidic gases as H.sub.2 S and CO.sub.2, water and hydrocarbons of more than two carbon atoms.
In order to overcome the above drawback, CN 1051166A and CN 1031072A disclose respectively the processes for preparing ethyl benzene from un-pre-refined ethylene raw material and the catalyst used therein. In the processes the ethylene raw material is only required containing no free water, H.sub.2 S content less than 6000 mg/m.sup.3 and C.sub.3.sup.= and C.sub.4.sup.= contents less than 2 vol %. The catalyst used is a Pentasil type zeolite catalyst comprising from 0.3 to 6 wt % of a mixture of rare earth elements or from 0.2 to 3 wt % of lanthanum, from 0.05 to 0.2 wt % of sulfur, from 30 to 70 wt % of zeolite and from 70 to 30 wt % of Al.sub.2 O.sub.3 having SiO.sub.2 /Al.sub.2 O.sub.3 ratio in the range of 40 to 100. Although the process for preparing ethyl benzene with this catalyst has solved the problem of the requirement for pre-refined raw material in the previous processes, the ethylene conversion is only in the range of 72.97 to 98.51 wt %, the ethyl benzene selectivity is only in the range of 76.84 to 89.89 wt %, the alkylation selectivity (as total amount of ethyl benzene and diethyl benzene produced) is also merely in the range of 98 to 99%. The single operation cycle for a catalyst is merely between 40 to 60 days, it means that the activity and stability of the catalyst are not sufficiently high.